The present proposal is a revision of a previous grant, MH45265, whose aim was to elucidate the neurobiology of positively motivated behaviors that are deficient in depressive illness. The goal of the project is to identify more precisely how these behaviors are disrupted during this disorder. Previous work on this grant has shown that brain epinephrine (EPI) and central alpha-1 adrenoceptors, both of which have been neglected in prior research on depression, play key roles in positively motivated behaviors in animals and are altered by stressors that are known to induce depressive behavior. Specifically these studies have suggested the hypotheses that brain EPI is the endogenous neurotransmitter for behaviorally activating alpha-1 receptors and that this "EPI/alpha-1 system" is specifically involved in positively- rather than negatively-motivated behaviors. These hypotheses will be tested in the present proposal by a combination of neuropharmacological, behavioral, immunohistochemical and neurochemical experiments that will assess the role of brain EPI as the endogenous stimulant of this system and the role of the system in various positively-motivated activities including self-stimulation of the lateral hypothalamus, conditioned approach and avoidance of positive and negative reinforcers, and effortful operant behavior. The research will likely identify the EPI/alpha-1 system as a new and important target for antidepressant and antistress medications